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不等式是刻画现实世界中量与量之间不等关系的数学模型,但是如何寻找不等关系呢?下面介绍几种方法.一、抓住关键词找不等关系例1(2013年呼和浩特)某次知识竞赛共有20道题,对于每道题,答对得10分,答错或不答都扣5分.小明要想使自己的得分超过90分,至少要答对多少道题?解析:根据关键词“超过”可以得到不等关系,从而可以列出不等式求解.设应答对x道题,根据题意,得10x-5(20-x)>90.解得x>122/3.x为整数,故x最小应为13.
Inequality is a mathematical model that characterizes the relationship between quantity and quantity in the real world, but how to find unequal relationships? Here are a few ways to describe them: 1. Grasp the key words to find unequal relationships Example 1 (2013, Hohhot) A total of 20 sub-knowledge contest questions, for each question, the answer is 10 points, wrong answer or do not answer all 5. Xiao Ming want to make his score over 90 points, at least to answer the question of how many? Analysis: According to the key Words “Exceeds ” can get unequal relations, which can be listed inequality solution set answer x questions, according to the motif, get 10x-5 (20-x)> 90. Solve x> 122/3. x is an integer, so x should be a minimum of 13.